There are two methods of making records unavailable in the system: One is to delete the record, the other is to de-activate the record. A de-activated record is not available for selection, but available for reporting. There are two reasons for de-activating and not deleting records:

(1) The system requires the record for auditing purposes.
(2) The record is referenced by other records. E.g., you cannot delete a Business Partner, if there are existing invoices for it. By de-activating the Business Partner you prevent it from being used in future transactions.

A more descriptive identifier (that does need to be unique) of a record/document that is used as a default search option along with the search key (that is unique and mostly shorter). It is up to 60 characters in length.